Method for making thermoplastic net-like product

ABSTRACT

This invention is concerned with a method of thermoplastic polymeric resin or resin adhesive deposition or adhesive bonding in which a thin film of thermoplastic resin with a special arrangement of slits or cuts is applied to a surface and heat is applied to bring the resin to heat-softened condition and cause the film to assume a pattern directly related to the arrangements of slits or cuts. The invention also relates to the open pattern resin or resin adhesive sheet resulting from heating of the cut or slit film.

0 United States Patent 1 1 1111 3,769,120

Chandler Oct. 30, 1973 [54] METHOD FOR MAKING TEERMOPLASTIC 3,474,95210/1969 Cover et a1. 161/109 X NELLIKE PRODUCT 3,092,439 6/1963 Harrison264/230 X 3,131,240 4 1964 Kirkpatrick.... 264 230 [75] Inventor: Edm ndA- C a Northwood, 3,199,284 8/1965 Scragg 161/D1G. 6 N.l-l. 3,400,188 91968 Olson 161/109 x 3,466,210 9/1969 Wareham.... 264/230 x [731 AsslgmeFrlbwrg, 3,253,317 '5/1966 Such 161/109 x Switzerland 22 F1 d: M 21,1971 I 1 l e ay Primary Examinerl-larold Ansher [21] Appl- NO: 1Attorney-Richard A. Wise et a1.

Related 0.8. Application Data Division of Ser. No. 733,576, May 31,1968, Pat. No. 3,616,152.

References Cited UNlTED STATES PATENTS 5/1969 Duns 156/85 [57] ABSTRACTThis invention is concerned with a method of thermoplastic polymericresin or resin adhesive deposition or adhesive bonding in which a thinfilm of thermoplastic resin with a special arrangement of slits or cutsis applied to a surface and heat is applied to bring the resin toheat-softened condition and cause the film to assume a pattern directlyrelated to the arrangements of slits or cuts. The invention also relatesto the open pattern resin or resin adhesive sheet resulting from heatingof the cut or slit film.

9 Claims, 7 Drawing Figures PAIENIEDucr 30 ms A L I 1 f'rzve nzor EdmondAC'handler Maw METHOD FOR MAKING THERMOPLASTIC NET-LIKE PRODUCT This isa divisional application of my copending application Ser. No. 733,576,filed May 31, 1968 entitled Resin Films, now U.S. Pat. No. 3,616,152,which issued Oct. 26, 1971.

FIELD OF THE INVENTION Adhesive processes for bonding articles, forexample, for bonding outsoles to shoe uppers are known in which a bandof thermoplastic synthetic polymeric resin adhesive is applied in moltenform to one of the attaching surfaces and, at the time the attaching isto be completed, the adhesive band is reheated and assembled against theheated attaching surface of the shoe upper. Excellent bonds areobtained; but the process requires the separate steps of applying moltenadhesive to the tread member to form an adhesive band and the furthersteps of reheating the adhesive and the surface which is to be placedagainst it. Also because of irregularities in the attaching surface, aband of adhesive of substantial thickness has been required.

Another procedure forming the subject of U.S. Pat. No. 3,483,581entitled Adhesive Processes, issued Dec. 16, 1969 in the names of EdmondA. Chandler and Kenelm W. Winslow, involves laying down a coherentadhesive sheet of thin interconnected strands of thermoplastic resinadhesive on-a surface to be bonded and thereafter heating the adhesivesheet and both of the surfaces which are to be joined by the adhesive.This procedure is effective to form strong bonds rapidly using a minimumamount of adhesive, however, the making of a sheet composed of thininterconnected strands introduces an element of expense and imposesrather difficult problems in forming a sheet of the desired uniformity.

It is an object of the present invention to provide a method of resindeposition or adhesive bonding using an inexpensive, uniform resin orresin adhesive sheet or film to deposit resin or adhesive in a regularuniform open pattern. The heating step may be used to activate theadhesive when an adhesive film is used and to preheat the surface onwhich the adhesive sheet is disposed.

It is a further object of the present invention to provide an openpattern thermoplastic resin or resin adhesive sheet.

To these ends and in accordance with a feature of the present invention,a thin sheet or film of thermoplastic polymeric resin with spaced cutsor slits arranged to give a pattern of resin on heating is disposed on asurface and subjected to heat. The large surface area of the sheet orfilm is effective to abosrb heat and when laid on a surface andsubjected to heat is converted by that heat to a regular open pattern.Where the film is an adhesive, the opening of the sheet to form the openpattern exposes to heat substantial portions of the surface on which itwas laid. After assembly and pressing of another surface against theheated adhesive and its associated surface, and cooling the assembly, astrong bond is obtained.

The invention will be described further in connection piece and showinga radiant heat source disposed to convert the film to an open pattern;

Fig. 2 is a plan view of the surface of the workpiece and the resin filmafter being heated to convert the film to an open pattern of resin film;

FIG. 3 is an elevational view of an assembly of a second workpiece witha workpiece carrying an open pattern of adhesive resin such as developedin FIG. 2;

FIG. 4 is a plan view of a second illustrative embodiment of theinvention with cuts disposed in a different pattern in the resin film;

FIG. 5 is a plan view showing the pattern of resin developed by heatingthe resin film of FIG. 4;

FIG. 6 is a plan view of another embodiment of the invention withparallel rows of slits arranged with slits opposite slits and uncutportions opposite uncut portions in the resin film; and

FIG. 7 is a plan view of the pattern of resin developed by heatingthe-resin film of FIG. 6.

As shown in the drawings, see FIGS. 1, 4 and 6, the novel sheet 10 is athin synthetic polymer resin film with spaced slits or cuts 12, 32 and42, respectively, so arranged that when the film is softened by heat,the film draws in at the edges of the slits or cuts to form an openpattern such as intersecting lines or beads 14 (FIG. 2) of softened,usually molten resin extending approximately along the median lines ofthe portions of the film between slits or cuts 12. The pattern orconfiguration of the resin is determined by the size, spacing andrelative position of the slits or cuts 12 in the initial adhesive film10. Although only three arrangements are shown, a wide variety ofpatterns or configurations of resin can be provided by arranging thespacing and relative position of the slits or cuts.

According to the method of the present invention the thermoplastic resinsheet 10 is supported on the surface 16 of a workpiece l7 and subjectedto heat to soften it and cause it to assume the desired open patternsuch as an intersecting line configuration. Since movement of the resinunder the action of heat is an important feature,'the sheet 10 is notclamped tightly between surfaces, but it is generally preferred that itbe merely supported on the surface 16 and subjected to a heat source 18such as radiant heat or hot gases in order that the movement of theresin not be restrained.

The sheet or film 10 can also be reduced to the open pattern by heatingit on a hot surface. While the supporting surface on which the sheet issubjected to heat is shown as the surface 16 of a workpiece to be bondedby the adhesive, it may be a release surface such as silicone orpolytetrafluoroethylene coated surface from which the resin may bestripped after heating to give it the desired configuration and coolingto solidify it. The open pattern sheet so obtained may be assembled withsurfaces to be bonded and activated to wet and adhere to those surfaces.On cooling such assembly a strong bond is obtained.

In general, thin films are converted to line patterns more readily thanthicker films and when the films are over about 0.03 inch, the openingeffect is not reliable. The width of film section between cuts shouldnot be over about 3/16 inch and with films of about 0.03 inch inthickness, the width should be not over about l/8 inch. It appearsimportant that the thickness of the film be not more than one-third,preferably considerably less than one-third the width of the spacebetween adjacent lines or cuts. Also in an arrangement of slits or cutsit is preferred that the length of the slits or cuts be at least equalto and preferably at least three times the greatest distance between anypoint on the edge of a slit or cut and the closest point on the slit orcut nearest the first mentioned point.

The term greatest distance between any point on the edge of a slit orcut and the closest point on the slit or cut nearest to the firstmentioned point" may be more readily understood from the followingdiscussion. From each point on a first slit or cut the distance can bemeasured to the closest point on the slit or out nearest to the firstmentioned point. The distances will be greater from some points on thefirst mentioned slit or cut to the slit or cut nearest to such points;and there will be one point on the slit or cut for which the distance tothe closest point on the slit or cut nearest to it will be greatest. Itis this greatest distance that is referred to above and in the claims byuse of the quoted language.

A preferred pattern of slits or cuts for an adhesive film is shown inFIG. 1 and comprises spaced parallel lines 20 of interrupted cuts 12with the cuts of one line 20 disposed opposite uncut portions 22 ofadjacent lines 20 of interrupted cuts and with the ends of the cuts ofone line overlapping the ends of the cuts of adjacent lines. Desirablythe end of a cut in one line may overlap the end of a cut in an adjacentline by from about 15 percent to about 40 percent of the length of thecut. This arrangement is particularly satisfactory since stresses,developed in the course of shrinking of the film may be relieved bymovement of the narrower portions of film between overlapping portionsof the cuts of adjacent rows of cuts. As shown in FIG. 2 a reticulatedpattern is formed on heating which comprises portions 24 of the lines 14corresponding to the segments of film between the ends of cuts in agiven line and portions 26 of the line 14 from the portions of filmwhere the slits or cuts of adjacent lines overlapped, which link theportions 24 to form a network.

The open pattern of heat softened adhesive provides a uniform effectivedistribution of the adhesive enabling good coverage with aminimumquantity of adhesive. When a second workpiece 27 (FIG. 3) is laid downon the heat softened adhesive and the workpieces are pressed together asshown in FIG. 3 the lines 24 and 26 of adhesive establish wettingcontact with the surfaces and give an excellent adhesiveness.

An alternative pattern of cuts is shown in FIG. 4 and comprises rows ofspaced parallel cuts or slits 32 extending in from the opposite edges28, 29 of a strip 30 of the adhesive sheet material leaving a centraluncut portion 31. As in the case of the adhesive film shown in FIG. 1and described above, it is desired that the length of the slits 32 be atleast equal to and preferably at least three times the width of thesegments 34, between adjacent parallel slits and it is important thatthe thickness of the adhesive film or sheet 10 be not more thanone-third the width of the segments 34 of adhesive film 30 betweenadjacent parallel slits 32. In the article shown in FIG. 4, the slits 32are arranged at an angle other than a right angle to the direction ofthe strip 30 of adhesive in order to provide a greater length of thesegments 34 relative to their width. On heating, the adhesive of thecentral uncut portion 31 of the strip forms a somewhat irregularbackbone 37, as shown in FIG. 5, while the adhesive of the segments 34forms angularly extending lines 39 somewhat in the nature of aherringbone pattern.

A further alternative form is shown in FIG. 6 in which spaced parallellines 42 of interrupted non-cut portions 44 are disposed in a strip 40so that the cuts 42 of one line are opposite the cuts of adjacent linesand uncut portions are opposite uncut portions. Heating such a stripresults in pulling-in of the adhesive to form openings 46, as shown inFIG. 7 which have some advantage in allowing gas trapped under the filmto escape. But this pattern of film does not offer the full advantage ofdeveloping lines or beads as in the forms of the adhesive sheet shown inFIGS. 1 and 4.

As the adhesive of which the sheet is formed, it is preferred to usehigh molecular weight thermoplastic synthetic polymer resin, forexample, relatively high molecular weight polyesters, polyamides,polyesteramides and thermoplastic polyester glycol urethanes orpolyether glycol urethanes. Other normally solid heatsoftenablepolymeric adhesive materials may be used which, either alone or inadmixture, can be formed into thin, nontacky films which retract onheating, and which are capable of melting to a condition for wetting andadhering surfaces to be joined and of hardening to provide an adhesivebond.

The following examples are given to aid in understanding the inventionbut it is to be understood that the invention is not limited to theparticular materials, dimensions or arrangements of cuts shown in theexamples nor to the particular procedures or conditions employed.

EXAMPLE I A polyamide from condensation of a mixture of percentdimerized linoleic acid and 15 mol percent of azelaic acid with amixture of diamines comprising 85 mol percent of ethylene diamine and 15mol percent of hexane diamine was formed into a thin film about 0.010inch in thickness. This polyamide had a softening point (Ball and Ring)of about 275 F. and a viscosity at 355 F. as determined with a 3/32 inchfalling steel ball of from 50 to 60 seconds. Parallel cuts were made inthe film in a pattern similar to that shown in FIG. 1 in which the slitswere about one-half inch long and adjacent lines of slits were spacedabout 3/32 inch.

A 1 inch wide strip of the material was disposed on the surface of apiece of butadiene styrene copolymer synthetic rubber shoe sole stockand was subjected to radiant heat at a distance of 2 inches for a periodof about 15 seconds. During the heating the film softened and shrank infrom the cut edges to form a reticulated pattern of lines of moltenadhesive as shown in FIG. 2. As the adhesive film shrank in, theunderlying portions of shoe sole stock were exposed to the radiant heatand brought to elevated temperature for effective union with theadhesive in subsequent steps.

At the same time the strip of stock with the adhesive film on itwas'subjected to heat, another piece of outsole stock was subjected tocomparable heating. Directly on completion of the heating steps thestrip of sole stock with the reticulated pattern of adhesive on it waspressed against the second piece of shoe sole stock to squeeze themolten adhesive and force it into wetting adhesive engagement with thesurfaces of each of thepieces of soling stock. On cooling of theassembly it was found that the pieces of soling stock were held togetherwith strength adequate for sole attaching.

EXAMPLE II A crystallizable copolyester was prepared by condensation andpolymerization of a 5.0:4.l:0.9 mol ratio mixture of terephthalic acid,isophthalic acid and dibutyl sebacate with 1,4 butane diol having amelting point of about 280 F. was formed into a 0.010 inch thickcontinuous film and the film was cut into strips 1 inch in width. Spacedparallel slits were cut in extending from opposite edges of the strip ofadhesive sheet material. The slits were spaced about 3/16 inch apart andwere exposed at an angle of about 45 to the direction of the stripleaving an uncut portion of the strip along the center about 3/16 inchwide as shown in FIG. 4.

A length of the adhesive film strip was disposed on the surface of apiece of outsole stock and was subjected to heating and assembled with aheated second section of outsole stock as in Example I. The heatedsections were pressed together with the adhesive between them. In theprocess of heating, the adhesive shrank in from the cut edges to formlines of molten adhesive arranged in a roughly herringbone pattern asshown in FIG. 5.

After assembly and pressing together of the strips, the strips wereallowed to cool. On cooling it was found that the strips were bondedtogether with a strength sufficient for outsole attaching on shoes.

EXAMPLE Ill A thermoplastic adhesive composition was preparedcomprisingabout 40 parts by weight of a polyterpene resin (Schenectady Resin ST 5115) having a melting point of 115 C. and understood to be a polymer ofbeta-pinene, 56 parts by weight of a resinous polyethylene and about 4parts by weight of butyl rubber. This adhesive composition had a fallingball viscosity as determined at 196 C. using a 3/16 inch steel ball offrom 40 to 50 seconds.

A 0.010 inch thick film was formed of this adhesive and the film wasslit in the same pattern as that used in FIG. 1.

A 1 inch wide strip of the slit film was disposed on paper and subjectedto radiant heat at a distance of 1 inch from the radiant heat source for15 seconds. The adhesive shrank to form a reticulated pattern comparableto that shown in FIG. 2. When a second piece of paper was pressedagainst the molten adhesive on the surface of the first piece, a strongbond was formed promptly. After cooling, the pieces of paper could notbe separated without destroying the paper.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent of the United States is:

l. A method for making a thermoplastic net-like product by forming apattern of slits or cuts through thermoplastic film or sheet and openingthe slits or cuts to form the product with openings forming a net-likepattern or configuration determined by the size, spacing and relativepositions of the slits or cuts; wherein the improvement comprisesforming said slits or cuts through a film or sheet made of athermoplastic which retracts or shrinks when heated with said slits orcuts arranged so that retraction or shrinkage of the portions of thefilm or sheet between the slits or cuts open the latter, supporting saidfilm or sheet by means-permitting all of its said portions to retract orshrink without substantial restraint and with at least one of its sidesurfaces exposed, applying heat to at least said exposed surface of saidfilm or sheet to heat said film or sheet to a degree causing its saidportions to retract or shrink to thereby open said slits or cuts andform said open or net-like pattern, and terminating said heatapplication so that said film or sheet subsequently hardens and saidproduct is obtained.

2. The method of claim 1 in which said film or sheet is in the form of astrip having a length greater than its width and said slits or cuts areelongated and arranged longitudinally with respect to said strip.

3. The method of claim-l in which said application of heat is bydirecting radiant heat to said exposed surface.

4. The method of claim 1 in which said application of heat is bydirecting a hot gas against said surface.

5. The method of claim 1 in which said film or strip has a thickness ofnot over about 0.03 inch.

6. The method of claim 1 in which said slits or cuts comprise spacedparallel lines of interrupted cuts with of the spaces between said linesof slits or cuts.

9. The method of claim 2 in which said slits comprise spaced parallellines of interrupted cuts with the cuts of 'one line disposed oppositeuncut portions of adjacent lines of interrupted cuts and with the endsof the cuts of one line overlapping the ends of the cuts of adjacentlines and said film or strip has a thickness of not over about 0.03inch.

2. The method of claim 1 in which said film or sheet is in the form of astrip having a length greater than its width and said slits or cuts areelongated and arranged longitudinally with respect to said strip.
 3. Themethod of claim 1 in which said application of heat is by directingradiant heat to said exposed surface.
 4. The method of claim 1 in whichsaid application of heat is by directing a hot gas against said surface.5. The method of claim 1 in which said film or strip has a thickness ofnot over about 0.03 inch.
 6. The method of claim 1 in which said slitsor cuts comprise spaced parallel lines of interrupted cuts with the cutsof one line disposed opposite uncut portions of adjacent lines ofinterrupted cuts and with the ends of the cuts of one line overlappingthe ends of the cuts of adjacent lines.
 7. The method of claim 5 inwhich the width of the film or sheet seCtions between said slits or cutsis not over about 1/8 inch in each instance.
 8. The method of claim 6 inwhich the thickness of said film or strip is not more than one-third thewidths of the spaces between said lines of slits or cuts.
 9. The methodof claim 2 in which said slits comprise spaced parallel lines ofinterrupted cuts with the cuts of one line disposed opposite uncutportions of adjacent lines of interrupted cuts and with the ends of thecuts of one line overlapping the ends of the cuts of adjacent lines andsaid film or strip has a thickness of not over about 0.03 inch.